[llvm] [ValueTracking] Support trunc nuw condition in isImpliedCondition (PR #141528)
Andreas Jonson via llvm-commits
llvm-commits at lists.llvm.org
Mon May 26 13:39:48 PDT 2025
https://github.com/andjo403 created https://github.com/llvm/llvm-project/pull/141528
Many trunc nuw conditions is implied/implies icmp instructions.
Proof: https://alive2.llvm.org/ce/z/oqQyxC
cc https://github.com/llvm/llvm-project/issues/134093
>From 6774f1623fd778b1fad98bf9842ac3359286555a Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 26 May 2025 21:45:24 +0200
Subject: [PATCH 1/4] [ValueTracking] Test trunc nuw condition in
isImpliedCondition (NFC)
---
.../select-safe-impliedcond-transforms.ll | 90 +++++++++++++++++++
1 file changed, 90 insertions(+)
diff --git a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
index 4b66b71773683..d8eda76cf649a 100644
--- a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
+++ b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
@@ -176,3 +176,93 @@ define i1 @a_false_implies_b_false2_comm(i8 %z, i1 %X, i1 %Y) {
%res = or i1 %sel, %a
ret i1 %res
}
+
+define i1 @trunc_nuw_implies_icmp_eq(i8 %x, i1 %c) {
+; CHECK-LABEL: @trunc_nuw_implies_icmp_eq(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[X:%.*]] to i1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 0
+; CHECK-NEXT: [[C:%.*]] = select i1 [[CMP]], i1 [[C1:%.*]], i1 false
+; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[TRUNC]], i1 true, i1 [[C]]
+; CHECK-NEXT: ret i1 [[SEL2]]
+;
+ %trunc = trunc nuw i8 %x to i1
+ %cmp = icmp eq i8 %x, 0
+ %sel1 = select i1 %cmp, i1 %c, i1 false
+ %sel2 = select i1 %trunc, i1 true, i1 %sel1
+ ret i1 %sel2
+}
+
+define i1 @icmp_eq_implies_trunc_nuw(i8 %x, i1 %c) {
+; CHECK-LABEL: @icmp_eq_implies_trunc_nuw(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[X:%.*]] to i1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 0
+; CHECK-NEXT: [[C:%.*]] = select i1 [[TRUNC]], i1 [[C1:%.*]], i1 false
+; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[CMP]], i1 true, i1 [[C]]
+; CHECK-NEXT: ret i1 [[SEL2]]
+;
+ %trunc = trunc nuw i8 %x to i1
+ %cmp = icmp eq i8 %x, 0
+ %sel1 = select i1 %trunc, i1 %c, i1 false
+ %sel2 = select i1 %cmp, i1 true, i1 %sel1
+ ret i1 %sel2
+}
+
+define <2 x i1> @trunc_nuw_implies_icmp_eq_vec(<2 x i8> %x, <2 x i1> %c) {
+; CHECK-LABEL: @trunc_nuw_implies_icmp_eq_vec(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw <2 x i8> [[X:%.*]] to <2 x i1>
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i8> [[X]], zeroinitializer
+; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[CMP]], <2 x i1> [[C1:%.*]], <2 x i1> zeroinitializer
+; CHECK-NEXT: [[SEL2:%.*]] = select <2 x i1> [[TRUNC]], <2 x i1> splat (i1 true), <2 x i1> [[C]]
+; CHECK-NEXT: ret <2 x i1> [[SEL2]]
+;
+ %trunc = trunc nuw <2 x i8> %x to <2 x i1>
+ %cmp = icmp eq <2 x i8> %x, splat (i8 0)
+ %sel1 = select <2 x i1> %cmp, <2 x i1> %c, <2 x i1> splat (i1 false)
+ %sel2 = select <2 x i1> %trunc, <2 x i1> splat (i1 true), <2 x i1> %sel1
+ ret <2 x i1> %sel2
+}
+
+define <2 x i1> @icmp_eq_implies_trunc_nuw_vec(<2 x i8> %x, <2 x i1> %c) {
+; CHECK-LABEL: @icmp_eq_implies_trunc_nuw_vec(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw <2 x i8> [[X:%.*]] to <2 x i1>
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i8> [[X]], zeroinitializer
+; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[TRUNC]], <2 x i1> [[C1:%.*]], <2 x i1> zeroinitializer
+; CHECK-NEXT: [[SEL2:%.*]] = select <2 x i1> [[CMP]], <2 x i1> splat (i1 true), <2 x i1> [[C]]
+; CHECK-NEXT: ret <2 x i1> [[SEL2]]
+;
+ %trunc = trunc nuw <2 x i8> %x to <2 x i1>
+ %cmp = icmp eq <2 x i8> %x, splat (i8 0)
+ %sel1 = select <2 x i1> %trunc, <2 x i1> %c, <2 x i1> splat (i1 false)
+ %sel2 = select <2 x i1> %cmp, <2 x i1> splat (i1 true), <2 x i1> %sel1
+ ret <2 x i1> %sel2
+}
+
+define i1 @neg_trunc_implies_icmp_eq(i8 %x, i1 %c) {
+; CHECK-LABEL: @neg_trunc_implies_icmp_eq(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X:%.*]] to i1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 0
+; CHECK-NEXT: [[SEL1:%.*]] = select i1 [[CMP]], i1 [[C:%.*]], i1 false
+; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[TRUNC]], i1 true, i1 [[SEL1]]
+; CHECK-NEXT: ret i1 [[SEL2]]
+;
+ %trunc = trunc i8 %x to i1
+ %cmp = icmp eq i8 %x, 0
+ %sel1 = select i1 %cmp, i1 %c, i1 false
+ %sel2 = select i1 %trunc, i1 true, i1 %sel1
+ ret i1 %sel2
+}
+
+define i1 @neg_icmp_eq_implies_trunc(i8 %x, i1 %c) {
+; CHECK-LABEL: @neg_icmp_eq_implies_trunc(
+; CHECK-NEXT: [[TRUNC:%.*]] = trunc i8 [[X:%.*]] to i1
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 0
+; CHECK-NEXT: [[SEL1:%.*]] = select i1 [[TRUNC]], i1 [[C:%.*]], i1 false
+; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[CMP]], i1 true, i1 [[SEL1]]
+; CHECK-NEXT: ret i1 [[SEL2]]
+;
+ %trunc = trunc i8 %x to i1
+ %cmp = icmp eq i8 %x, 0
+ %sel1 = select i1 %trunc, i1 %c, i1 false
+ %sel2 = select i1 %cmp, i1 true, i1 %sel1
+ ret i1 %sel2
+}
>From bd6627cfc74a0db56be3f0626a05cee78cd84f65 Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 26 May 2025 21:49:04 +0200
Subject: [PATCH 2/4] [ValueTracking] Decompose ICmpInst argument in
isImpliedCondICmps (NFC)
---
llvm/lib/Analysis/ValueTracking.cpp | 19 +++++++++----------
1 file changed, 9 insertions(+), 10 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 5b9338b500ecc..942b5f5dc8c98 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -9165,15 +9165,13 @@ isImpliedCondCommonOperandWithCR(CmpPredicate LPred, const ConstantRange &LCR,
/// is true. Return false if LHS implies RHS is false. Otherwise, return
/// std::nullopt if we can't infer anything.
static std::optional<bool>
-isImpliedCondICmps(const ICmpInst *LHS, CmpPredicate RPred, const Value *R0,
- const Value *R1, const DataLayout &DL, bool LHSIsTrue) {
- Value *L0 = LHS->getOperand(0);
- Value *L1 = LHS->getOperand(1);
-
+isImpliedCondICmps(CmpPredicate LPred, const Value *L0, const Value *L1,
+ CmpPredicate RPred, const Value *R0, const Value *R1,
+ const DataLayout &DL, bool LHSIsTrue) {
// The rest of the logic assumes the LHS condition is true. If that's not the
// case, invert the predicate to make it so.
- CmpPredicate LPred =
- LHSIsTrue ? LHS->getCmpPredicate() : LHS->getInverseCmpPredicate();
+ if (!LHSIsTrue)
+ LPred = ICmpInst::getInverseCmpPredicate(LPred);
// We can have non-canonical operands, so try to normalize any common operand
// to L0/R0.
@@ -9314,9 +9312,10 @@ llvm::isImpliedCondition(const Value *LHS, CmpPredicate RHSPred,
LHSIsTrue = !LHSIsTrue;
// Both LHS and RHS are icmps.
- const ICmpInst *LHSCmp = dyn_cast<ICmpInst>(LHS);
- if (LHSCmp)
- return isImpliedCondICmps(LHSCmp, RHSPred, RHSOp0, RHSOp1, DL, LHSIsTrue);
+ if (const auto *LHSCmp = dyn_cast<ICmpInst>(LHS))
+ return isImpliedCondICmps(LHSCmp->getCmpPredicate(), LHSCmp->getOperand(0),
+ LHSCmp->getOperand(1), RHSPred, RHSOp0, RHSOp1,
+ DL, LHSIsTrue);
/// The LHS should be an 'or', 'and', or a 'select' instruction. We expect
/// the RHS to be an icmp.
>From 701603f6d755b54cf559fc1184c7037b397ec70f Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 26 May 2025 22:00:57 +0200
Subject: [PATCH 3/4] [ValueTracking] Support trunc nuw condition in
isImpliedCondition LHS argument.
---
llvm/lib/Analysis/ValueTracking.cpp | 5 +++++
.../InstCombine/select-safe-impliedcond-transforms.ll | 8 ++------
2 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 942b5f5dc8c98..d585b55f02401 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -9316,6 +9316,11 @@ llvm::isImpliedCondition(const Value *LHS, CmpPredicate RHSPred,
return isImpliedCondICmps(LHSCmp->getCmpPredicate(), LHSCmp->getOperand(0),
LHSCmp->getOperand(1), RHSPred, RHSOp0, RHSOp1,
DL, LHSIsTrue);
+ const Value *V;
+ if (match(LHS, m_NUWTrunc(m_Value(V))))
+ return isImpliedCondICmps(CmpInst::ICMP_NE, V,
+ ConstantInt::get(V->getType(), 0), RHSPred,
+ RHSOp0, RHSOp1, DL, LHSIsTrue);
/// The LHS should be an 'or', 'and', or a 'select' instruction. We expect
/// the RHS to be an icmp.
diff --git a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
index d8eda76cf649a..517bbad90dc30 100644
--- a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
+++ b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
@@ -180,9 +180,7 @@ define i1 @a_false_implies_b_false2_comm(i8 %z, i1 %X, i1 %Y) {
define i1 @trunc_nuw_implies_icmp_eq(i8 %x, i1 %c) {
; CHECK-LABEL: @trunc_nuw_implies_icmp_eq(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[X:%.*]] to i1
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 0
-; CHECK-NEXT: [[C:%.*]] = select i1 [[CMP]], i1 [[C1:%.*]], i1 false
-; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[TRUNC]], i1 true, i1 [[C]]
+; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[TRUNC]], i1 true, i1 [[C:%.*]]
; CHECK-NEXT: ret i1 [[SEL2]]
;
%trunc = trunc nuw i8 %x to i1
@@ -210,9 +208,7 @@ define i1 @icmp_eq_implies_trunc_nuw(i8 %x, i1 %c) {
define <2 x i1> @trunc_nuw_implies_icmp_eq_vec(<2 x i8> %x, <2 x i1> %c) {
; CHECK-LABEL: @trunc_nuw_implies_icmp_eq_vec(
; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw <2 x i8> [[X:%.*]] to <2 x i1>
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i8> [[X]], zeroinitializer
-; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[CMP]], <2 x i1> [[C1:%.*]], <2 x i1> zeroinitializer
-; CHECK-NEXT: [[SEL2:%.*]] = select <2 x i1> [[TRUNC]], <2 x i1> splat (i1 true), <2 x i1> [[C]]
+; CHECK-NEXT: [[SEL2:%.*]] = select <2 x i1> [[TRUNC]], <2 x i1> splat (i1 true), <2 x i1> [[C:%.*]]
; CHECK-NEXT: ret <2 x i1> [[SEL2]]
;
%trunc = trunc nuw <2 x i8> %x to <2 x i1>
>From e35a12f95c5b860dfac8d7013f96100089a9255e Mon Sep 17 00:00:00 2001
From: Andreas Jonson <andjo403 at hotmail.com>
Date: Mon, 26 May 2025 22:10:52 +0200
Subject: [PATCH 4/4] [ValueTracking] Support trunc nuw condition in
isImpliedCondition RHS argument.
---
llvm/lib/Analysis/ValueTracking.cpp | 9 +++++++++
.../select-safe-impliedcond-transforms.ll | 12 ++++--------
2 files changed, 13 insertions(+), 8 deletions(-)
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index d585b55f02401..b7084cf3619f3 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -9358,6 +9358,15 @@ std::optional<bool> llvm::isImpliedCondition(const Value *LHS, const Value *RHS,
return std::nullopt;
}
+ const Value *V;
+ if (match(RHS, m_NUWTrunc(m_Value(V)))) {
+ if (auto Implied = isImpliedCondition(LHS, CmpInst::ICMP_NE, V,
+ ConstantInt::get(V->getType(), 0), DL,
+ LHSIsTrue, Depth))
+ return InvertRHS ? !*Implied : *Implied;
+ return std::nullopt;
+ }
+
if (Depth == MaxAnalysisRecursionDepth)
return std::nullopt;
diff --git a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
index 517bbad90dc30..ba34930dc14c1 100644
--- a/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
+++ b/llvm/test/Transforms/InstCombine/select-safe-impliedcond-transforms.ll
@@ -192,10 +192,8 @@ define i1 @trunc_nuw_implies_icmp_eq(i8 %x, i1 %c) {
define i1 @icmp_eq_implies_trunc_nuw(i8 %x, i1 %c) {
; CHECK-LABEL: @icmp_eq_implies_trunc_nuw(
-; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw i8 [[X:%.*]] to i1
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X]], 0
-; CHECK-NEXT: [[C:%.*]] = select i1 [[TRUNC]], i1 [[C1:%.*]], i1 false
-; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[CMP]], i1 true, i1 [[C]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq i8 [[X:%.*]], 0
+; CHECK-NEXT: [[SEL2:%.*]] = select i1 [[CMP]], i1 true, i1 [[C:%.*]]
; CHECK-NEXT: ret i1 [[SEL2]]
;
%trunc = trunc nuw i8 %x to i1
@@ -220,10 +218,8 @@ define <2 x i1> @trunc_nuw_implies_icmp_eq_vec(<2 x i8> %x, <2 x i1> %c) {
define <2 x i1> @icmp_eq_implies_trunc_nuw_vec(<2 x i8> %x, <2 x i1> %c) {
; CHECK-LABEL: @icmp_eq_implies_trunc_nuw_vec(
-; CHECK-NEXT: [[TRUNC:%.*]] = trunc nuw <2 x i8> [[X:%.*]] to <2 x i1>
-; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i8> [[X]], zeroinitializer
-; CHECK-NEXT: [[C:%.*]] = select <2 x i1> [[TRUNC]], <2 x i1> [[C1:%.*]], <2 x i1> zeroinitializer
-; CHECK-NEXT: [[SEL2:%.*]] = select <2 x i1> [[CMP]], <2 x i1> splat (i1 true), <2 x i1> [[C]]
+; CHECK-NEXT: [[CMP:%.*]] = icmp eq <2 x i8> [[X:%.*]], zeroinitializer
+; CHECK-NEXT: [[SEL2:%.*]] = select <2 x i1> [[CMP]], <2 x i1> splat (i1 true), <2 x i1> [[C:%.*]]
; CHECK-NEXT: ret <2 x i1> [[SEL2]]
;
%trunc = trunc nuw <2 x i8> %x to <2 x i1>
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